Apparatus and method for flow equipartition

ABSTRACT

A system includes a first pressure-adjusting device positioned in a first line and a second pressure-adjusting device positioned in a second line. The first pressure-adjusting device is actuated solely via a first pneumatic signal output from a first pilot valve to control a downstream pressure in the first line. The second pressure-adjusting device is actuated via the first pneumatic signal in a first mode of operation, and is actuated via a second pneumatic signal output from a second pilot valve in a second mode of operation to control a downstream pressure in the second line.

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is claimed to U.S. patent application Ser. No. 15/106,405,filed on Jun. 20, 2016, which is a National Stage entry ofPCT/IB15/51939, filed on Mar. 17, 2015, the entire contents of which areincorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to the distribution of gas and,more particularly, to an equipartition apparatus for systems or stationsfor adjusting pressure exerted on two or more lines.

BACKGROUND

The systems or stations for adjusting the pressure on several lines areessentially plants which allow networks to be fed for carrying anddistributing gas to civil and industrial users. Purely by way ofexample, systems for adjusting the pressure are used in distributionnetworks for reducing the gas pressure from medium pressure to lowpressure.

With reference to the general current standards, the term “low feedpressure” is defined as a pressure between approximately 0.04 bar andapproximately 12 bar, “medium feed pressure” is defined as a pressurebetween approximately 12 bar and approximately 24 bar, and aboveapproximately 24 bar is defined as “high pressure”.

The reference to “two or more lines” in the above-mentioned adjustingsystems refers to the fact that these adjusting systems typically caninclude several pressure-adjusting lines arranged in parallel. Of theselines, one is generally referred to as “main”, as it is normallyoperational, and the others are referred to as “secondary”, as this lineis normally inactive and designed to enter into operation in the case ofa fault or malfunction of the main line.

The main and secondary lines are calibrated differently and, if the mainline is no longer able to feed gas at the calibration pressure, thesecondary lines activate automatically, feeding gas at the relativecalibration pressure, which is lower than that of the main line.

Existing devices designed to manage the equipartition of the flowbetween various lines in parallel have substantial drawbacks. Forexample, these devices require, so as to be able to control theadjusting devices of the various lines, one or more additional controlunits, thereby complicating the architecture of the adjusting system andconsequently increasing both the plant and management costs. Anotherdrawback is due to the impossibility of guaranteeing, at least in thecase of a fault on the main line, an adequate and safe operation of theremaining parts of the plant. Another drawback resulting from theintroduction of additional control units, in addition to the managementcomplexity, is due to the need to alter the existing service parameterssuch as, for example, the calibration values of the original controlunits.

SUMMARY

In accordance with a first aspect, a system includes a firstpressure-adjusting device positioned in a first line and a secondpressure-adjusting device positioned in a second line. The firstpressure-adjusting device is actuated solely via a first pneumaticsignal output from a first pilot valve to control a downstream pressurein the first line. The second pressure-adjusting device is actuated viathe first pneumatic signal in a first mode of operation, and is actuatedvia a second pneumatic signal output from a second pilot valve in asecond mode of operation to control a downstream pressure in the secondline. In some examples, in the second mode of operation, the downstreampressure in the second line is less than the downstream pressure in thefirst line.

In some approaches, the system may additionally include a pneumaticconnection conduit that connects the first pilot valve and the secondpressure-adjusting device to determine a pressure equal to thedownstream pressure in the first line. Further, the system may include apneumatic switch positioned along the pneumatic connection conduit. Thepneumatic switch is adapted to interrupt the connection between thefirst pilot valve and the second pressure-adjusting device. Thepneumatic switch may also be configured to remain normally open fordownstream pressure values in the first line that are greater than orequal to a first predetermined pressure determined by the first pilotvalve or a second predetermined pressure determined by the second pilotvalve.

In some examples, the system may include a controller that controls thepneumatic switch by selectively activating closure of the pneumaticswitch. The controller may be a pneumatic controller and may include apneumatic feeding conduit to feed the pneumatic switch. The pneumaticfeeding conduit is connected to the first line to feed gas thereto. Thepneumatic switch may include a membrane and a spring. The spring may beadapted to oppose a force generated by action of the gas pressure actingon the membrane.

In some examples, the controller may be in the form of an electricalcontroller that includes a pressure sensor positioned along the firstline for feeding gas thereto, an electric actuator positioned inside thepneumatic switch, and an electrical circuit connecting the sensor andthe electric actuator. The circuit may include a control unit toactivate the electric actuator and close the pneumatic switch when thesensor detects, on the first line, a pressure value less than a firstpredetermined pressure determined by the first pilot valve.

In accordance with a second aspect, a method includes positioning afirst pressure-adjusting device in a first line, and positioning asecond pressure-adjusting device in a second line. The firstpressure-adjusting device is actuated solely via a first pneumaticsignal that is output from a first pilot valve to control a downstreampressure in the first line. The second pressure-adjusting device isactuated via the first pneumatic signal in a first mode of operation andvia a second pneumatic signal that is output from a second pilot valvein a second mode of operation to control a downstream pressure in thesecond line.

In accordance with a third aspect, a method for controlling a systemhaving a first pressure-adjusting device positioned in a first line, asecond pressure-adjusting device positioned in a second line, a firstpilot valve that outputs a first signal, and a second pilot valve thatoutputs a second signal is provided. The method includes controlling adownstream pressure in the first line by actuating the firstpressure-adjusting device solely via the first pneumatic signal outputfrom the first pilot valve. In a first mode of operation, a downstreampressure in the second line is controlled by actuating the secondpressure-adjusting device via the first pneumatic signal output from thefirst pilot valve. In a second mode of operation, the downstreampressure in the second line is controlled by actuating the secondpressure-adjusting device via the second pneumatic signal output fromthe second pilot valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The above needs are at least partially met through provision of theapparatus and method for flow equipartition described in the followingdetailed description, particularly when studied in conjunction with thedrawings, wherein:

FIG. 1 is a schematic view of a preferred embodiment of the apparatus inaccordance with various embodiments;

FIG. 2 is a schematic view of a variant embodiment of the apparatus ofFIG. 1 in accordance with various embodiments;

FIG. 3 is a schematic view of a further variant embodiment of theapparatus of FIG. 1 in accordance with various embodiments; and

FIG. 4 is a schematic view of a further variant embodiment of theapparatus of FIG. 1 in accordance with various embodiments.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions and/or relative positioningof some of the elements in the figures may be exaggerated relative toother elements to help to improve understanding of various embodimentsof the present invention. Also, common but well-understood elements thatare useful or necessary in a commercially feasible embodiment are oftennot depicted in order to facilitate a less obstructed view of thesevarious embodiments. It will further be appreciated that certain actionsand/or steps may be described or depicted in a particular order ofoccurrence while those skilled in the art will understand that suchspecificity with respect to sequence is not actually required. It willalso be understood that the terms and expressions used herein have theordinary technical meaning as is accorded to such terms and expressionsby persons skilled in the technical field as set forth above exceptwhere different specific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION

Generally speaking, pursuant to these various embodiments, anequipartition apparatus is provided which is able to operate effectivelyand safely in the case of a fault or malfunction on one of the gas feedlines, without outside energy sources, and which is also inexpensive tomake. Another aim of this invention is to provide a method forequipartition of the gas flow between two feed lines which is practical,simple to manage and efficient. The above-mentioned aims are achievedaccording to this invention by an apparatus and method for equipartitionof the flow of gas comprising the technical features described in theappended claims.

Gas distribution firms are implementing low cost and fully automaticapparatuses for equipartition of the flow that allow the two or moreexisting lines to always run in parallel with a flow of gasequipartitioned and substantially equal. In short, this modificationtheoretically allows the achievement of many advantages. A firstadvantage is a considerable lowering of the noise level since the flowof gas would be divided between several lines. Another advantage isalways having in operation the lines, to prevent the problems ofsticking of the seals (O-rings) which sometimes occurs when, following afault on the main line, an emergency line (secondary) must interveneafter long periods of inactivity. The problem of sticking of the O-ringsis caused by the prolonged inactivity of the apparatuses, a problemwhich would be resolved by making the lines normally operating.

Another advantage that would be achieved by making several lines operatein parallel would be that of not having to design the lines to operate,for example in the case of two lines, one at 100% and the other at forexample 70% but it might, instead, be possible to design both lines toeach cover 50% of the total flow. In this way there would beconsiderable savings also in terms of costs and installation spaces,moreover being able to overcome any faults in the lines by adopting agrid architecture of the current gas distribution networks.

With reference to the accompanying drawings, the numeral 100 denotes inits entirety an apparatus for equipartition of the flow between severalgas feed lines. With reference to FIG. 1, the numeral 1 denotes asection of a first line for feeding gas hereafter also referred to asthe main line. Numeral 2, on the hand, denotes a section of a secondline for feeding gas, parallel to the above-mentioned first line 1,hereinafter also referred to as the secondary line. Respective arrowsindicate the direction of travel of the gas along the lines 1, 2.

With reference to the first line 1, along the section illustrated thereare, one after the other, two devices 3, 4, of substantially known type,for adjusting the pressure. The adjusting device 3 positioned upstreamrelative to the above-mentioned direction of travel is a reserve devicewhilst the adjusting device 4 positioned downstream is the one normallyoperating, which therefore adjusts the pressure of the gas passingthrough it. The adjusting device 4 positioned downstream will bereferred to hereinafter also as the first adjusting device.

Similarly, with reference to the second line 2, along the illustratedsection there are, one after the other, two respective devices 5, 6, foradjusting the pressure, also of substantially known type. The adjustingdevice 5 positioned upstream, relative to the above-mentioned directionof travel, is a reserve device whilst the adjusting device 6 positioneddownstream is the one normally operating, which therefore adjusts thepressure of the gas passing through it. The adjusting device 6positioned downstream will be referred to hereinafter also as the secondadjusting device. The above-mentioned pressure-adjusting devices 3, 4,5, 6 contribute to defining, on the lines 1, 2, a pressure-adjustingsystem.

Purely by way of an example, assuming to be at a so-called finaladjusting system, which receives the gas from pipes at a low-pressurefor distribution to networks for feeding users, it can be consideredthat, upstream of the adjusting devices 3, 5, the gas pressure isapproximately 5 bar whilst downstream of the first and second adjustingdevice 4, 6 it is in the order of 20 mbar. 15 These values are givenpurely by way of an example and do not limit the scope of theapplication.

For each of the pressure-adjusting devices 3, 4, 5, 6, the apparatusaccording to this invention comprises a respective control unit 7, 8, 9,10. The control units 7, 8, 9, 10 are of substantially known type andare actuated pneumatically using the difference in pressure of the gasbetween upstream and downstream of the pressure-adjusting devices 3, 4,5, 6. Each control unit 7, 8, 9, 10 is connected to the respectiveadjusting device 3, 4, 5, 6 by a respective drive conduit 7 a, 8 a, 9 a,10 a.

In the following description, the control units 8, 10 of the first andsecond pressure-adjusting device 4, 6 will also be indicated,respectively, as the first control unit 8 and the second control unit10. The apparatus 100 for equipartition of the flow between several gassupply lines comprises a number of control units 7, 8, 9, 10 equal tothe number of pressure-adjusting devices 3, 4, 5, 6 present on the lines1 and 2. In other words, this means that the apparatus 100 does notinclude any auxiliary control unit other than those relative to eachpressure-adjusting device 3, 4, 5, 6.

The safety regulations regarding gas distribution require that eachpressure-adjusting device be associated with a relative control unit.The assembly described herein is also normally subjected to testing.

Each feed line 1, 2 also comprises a respective actuating conduit 11, 12for driving the control units 7, 8, 9, 10. On the first line 1,downstream of the first adjusting device 4, there is a pressure pick-uppoint 13. From this point, 13, advantageously integrating a manifold 14,a plurality of pipes 15 extend, designed to transmit the measuredpressure value (normally P1) to the various devices forming part of theadjusting system on the line 1.

Similarly to the discussion with reference to the first line 1, on the15 second line 2, downstream of the second adjusting device 6, there isa pressure pick-up point 16. From this point 16, advantageouslyintegrating a manifold 17, a plurality of pipes 18 extend, designed totransmit the measured pressure value to the various devices forming partof the adjusting system on the line 2. In particular, both thepressure-adjusting devices 3, 4, 5, 6 and the relative control units 7,8, 9, 10 need, in known manner, for the correct operation, to receive asignal representing the pressure value downstream of the first andsecond adjusting device 4, 6.

One approach to transmitting this value is that of placing directly incommunication each of the above-mentioned adjusting devices and controlunits with the gas on the respective line, downstream of the adjustingdevice 4, 6. As illustrated in FIG. 1, the equipartition apparatus 100comprises a pneumatic conduit 19 for connecting the first control unit 8of the first adjusting device 4 with the second adjusting device 6, todetermine in the second line 2, downstream of the second adjustingdevice 6, a pressure P1 equal to that adjusted on the first line 1.

In practice, the pneumatic conduit 19 connects the conduit 8 a with theconduit 10 a, effectively excluding the control unit 10 from the controlof the second adjusting device 6, thanks to the calibration pressure P2of the unit 10 which is less than the calibration pressure P1 of theunit 8. In other words, by means of the pneumatic connection conduit 19,the control unit 8 of the first adjusting device 4 also controls thesecond adjusting device 6, effectively equipartitioning the pressure ofthe gas passing along the two lines 1, 2 downstream of the apparatus100.

As illustrated in FIG. 1, the equipartition apparatus 100 comprises anautomatic pneumatic switch 20 positioned along the pneumatic connectionconduit 19. The pneumatic switch 20 is designed to interrupt thepneumatic connection between the first control unit 8 and the seconddevice 6 for adjusting the pressure of the second line 2. As illustratedin FIG. 1, the apparatus 100 comprises a pneumatic conduit 21 forfeeding the switch 20. The switch 20 is therefore a pneumaticallyoperated pneumatic switch. The pneumatic feeding conduit 21 is connectedto the first gas feed line 1, downstream of the first adjusting device4, in a zone subjected normally to the above-mentioned firstpredetermined pressure P1. Advantageously, the pneumatic conduit 21 isconnected to the manifold 14 defining the above-mentioned pick-up point13. Further, the pneumatic switch 20 comprises a membrane 20 a and aspring 20 b opposing the force generated by the action of the 25 gaspressure acting on the membrane 20 a.

The above-mentioned pneumatic feeding conduit 21 defines for theapparatus 100 means of a pneumatic type for controlling the pneumaticswitch 20. In the variant embodiment illustrated in FIG. 2, theequipartition 30 apparatus 100 comprises, as an alternative to theswitch 20 described above, a pneumatic switch 20 e actuatedelectrically, inside an electrical circuit 22. The electrical circuit 22comprises a pressure sensor 23 positioned along the main line 1 formeasuring the pressure value existing on the main line 1 downstream ofthe first adjusting device 4, a value which is normally that of thepressure P1 determined by the first control unit 8.

The pressure sensor 23 transforms the measured pressure value into anelectrical signal which through the circuit 22 reaches a control unit 24that operates the pneumatic switch 20 e actuated electrically. Moreprecisely, according to a preferred embodiment, the control unit 24controls an electric actuator 20 f contained inside the switch 20 e andopposed by a spring which, in the absence of the action of the actuator20 f, would tend to close the switch 20 e, that is, interrupt theconnecting conduit 19. This circumstance is equivalent, as describedabove, to interrupting the 15 pneumatic connection between the firstcontrol unit 8 and the second device 6 for adjusting the pressure of thesecond line 2.

The above-mentioned pressure sensor 23, electrical connecting circuit 22and control unit 24 define, in their entirety, electrical means ofcontrolling the pneumatic switch 20 e.

In the variant embodiment illustrated in FIG. 3, the equipartitionapparatus 100 operates on three lines 1, 2, 2′ for feeding the gas. Withregard to the component elements of the lines 1 and 2, reference shouldbe made to the above description regarding FIG. 1. The line 2′ is also asecondary line like the line 2 described above. The component elementsof the line 2′ corresponding and equivalent to elements alreadyindicated with reference to the line 2, are denoted with the samenumerical reference differentiated solely by an apex as in the case of 2and 2′ indicated above.

In the apparatus 100 illustrated in FIG. 3, the conduit 19 connects the30 control unit 8 of the first adjusting device 4 with the secondadjusting device 6 and also with a third adjusting device 6′ of thethird line 2′, to determine, both in the second line 2, downstream ofthe second adjusting device 6, and in the third line 2′, downstream ofthe third adjusting device 6′, a same pressure P1 equal to that adjustedon the first line 1. In this case, the pneumatic conduit 19 connects theconduit 8 a both with the conduit 10 a and with the conduit 10′a,effectively excluding both the control unit 10 from the control of thesecond adjusting device 6, and the control unit 10′ from the control ofthe third adjusting device 6′, thanks to the fact that both thecalibration pressure P2 of the unit 10 and the calibration pressure P3of the unit 10′ are less than the calibration pressure P1 of the unit 8.

In other words, by means of the pneumatic connection conduit 19 thecontrol unit 8 of the first adjusting device 4 also controls the furtheradjusting devices 6, 6′, effectively equipartitioning the pressure ofthe gas passing along all the lines 1, 2, 2′ downstream of the apparatus100.

In use, with reference to the diagram shown in FIG. 1, during normaloperation, the first control unit 8 of the first device 4 for adjustingthe pressure of the main line 1 also controls the second device 6 foradjusting the pressure of the secondary line 2. In this way, both thelines 1, 2 feed gas downstream at the same calibration pressure P1 asthe first control unit 8. This, as mentioned, occurs under normaloperation of the equipartition apparatus 100, where, precisely, the flowof gas is equally distributed between the main line 1 and the secondaryline 2.

The automatic pneumatic switch 20, calibrated at a pressure Pv slightlyless than P1, is therefore normally active, that is to say, open,allowing the pneumatic connection between the first control unit 8 andthe second device 6 for adjusting the pressure of the secondary line 2,through the connecting conduit 19. In this normal operating condition,the second control unit 10 associated with the second device 6 foradjusting the pressure of the second line 2 is inactive (but designed todetermine, when active, downstream of the second adjusting device 6, asecond pressure P2 less than both the pressure P1 and the calibrationpressure Pv of the pneumatic switch). If there is a fault or amalfunction on the main line, such as to determine downstream of theadjusting device a lowering of the pressure to a value PO which is alsoconsiderably less than the calibration value P1 of the first controlunit 8, the pressure PO is established immediately also within thepneumatic switch 20.

In short, the above-mentioned lowering of pressure along the main line 1can result from a drawing of gas by users downstream, which is not 10supported by a suitable feed flow; this circumstance usually occurringdue to a blockage caused by a fault. Since the pneumatic switch 20 iscalibrated at a pressure Pv just less than the value P1, it deactivatesimmediately (when it reaches the pressure PO significantly less thanP1), thus interrupting the pneumatic conduit 19 for connecting betweenthe first control unit 8 and the second device 6 for adjusting thepressure of the secondary line 2.

Following this interruption, the second control unit 10 becomes activeon the second pressure-adjusting device 6, imposing on the adjustingdevice 6 a relative calibration pressure P2, less than both P1 and Pv.In this way, following the modified command on the second adjustingdevice 6, the new pressure P2, which is less than the pressure P1existing on both the lines 1, 2 for feeding the gas when both wereoperating, is created on the second line 2.

The operation of the apparatuses 100 illustrated in FIGS. 2 and 3 is notunlike that just described with reference to FIG. 1. With regard to theembodiment shown in FIG. 2, the pneumatic switch 20 e actuatedelectrically is activated by the respective control unit 24 as afunction of the pressure value measured by the pressure sensor 23.However, in the embodiment of FIG. 3 there are two pneumatic switches 3020, 20′, each acting on the connecting conduit 19 and controlled by thepressure measured respectively at the pick-up points 13 and 16.

The switch 20 is designed to interrupt the connecting conduit 19 in thecase of lowering of the pressure on the line 1, while the switch 20′ isdesigned to interrupt the connecting conduit 19 in the case of loweringof the pressure on the line 2. Similarly to what is described aboveregarding calibration of the pneumatic switch 20 at a pressure Pvslightly less than the value P1, in the case of the pneumatic switch20′, it is calibrated at a pressure P′v slightly less than the value P2and in any case greater than P3. In this way, following a fault on theline 1, the calibration pressure P2 of the second control unit 10 isestablished on the line 2 and the same occurs on the third line 2′,operating the second control unit 10, through the lower section of theconduit 19, also on the third adjusting device 6′. When, the other hand,a fault also occurs on the second line 2, the switch 20′ will interruptthe conduit 19 and the second adjusting device 6′ will be adjusted bythe respective control unit 10′ that will impose the relativecalibration pressure P3 on the third line 2′.

In the variant embodiment illustrated in FIG. 4, the equipartitionapparatus 100 comprises a pneumatic conduit R for connecting thepneumatic switch 20 to the conduit 7 a for driving the standbypressure-adjusting device 3 of the main line, the conduit beinginterposed between the control unit 7 and the standby pressure-adjustingdevice 3. The pneumatic switch 20 is therefore driven by the pressureexisting in the conduit 7 a for driving the standby pressure-adjustingdevice 3.

According to the embodiments illustrated in FIGS. 1 to 3, the pneumaticswitch 20, driven by the pressure existing in the manifold 14,interrupts the pneumatic conduit 19 for connecting between the firstcontrol unit 8 and the second pressure-adjusting device 6 following acomplete malfunction on the main line, this malfunction consistingbasically in a block (closure) of the line itself. In the variantembodiment of FIG. 4, on the other hand, the pneumatic switch 20interrupts the pneumatic conduit 19 when the standby pressure-adjustingdevice 3 intervenes. In other words, the pneumatic switch 20 intervenesfollowing a malfunction of the device 4 of the main line 1 such as tocause the intervention of the standby pres sure-adjusting device 3 ofthe main line 1, but not necessarily the block of the dispensing of gasof that line 1.

By actuating the above-mentioned operation, the equipartition apparatus100 according to this invention, in its many alternative embodiments,brings important advantages. A first of these advantages is due to thefact that the devices 4, 6, 6′ for 10 adjusting the various lines do notrequire, for their control, control units in addition to those alreadyusually provided on each feed line. Another advantage is thepossibility, in the event of a fault on the main line of guaranteeing anadequate and safe operation of the remaining lines 2′ even though atslightly reduced pressures. Another advantage achieved by the apparatus100 for equipartition of the pressure according to this invention is thefact that the original service parameters of the individual lines can bemaintained, such as, for example, the calibration pressure values P1,P2, P3 of the original control units already present on the lines 1, 2,2′ regardless of their operation in equipartition mode.

Another advantage, specifically for the embodiments illustrated in FIGS.1 and 3, that is to say, having pneumatically operated pneumaticswitches 20, 20, is that of not requiring, for their operation, anyenergy supply other than the energy of the gas pressure carried by thelines 1, 2, 2′. In other words, unlike equipartition apparatuses ofknown type, the apparatus according to this invention in its embodimentswhich adopt a pneumatically operated pneumatic switch 20, 21, does notneed for its correct operation any source of external energy (forexample to supply a solenoid valve).

The system and method described above is susceptible of industrialapplication and may be modified and adapted in several ways (such as,for example, in the equipartition of the flow between high pressurelines) without thereby departing from the scope of the inventiveconcept. Moreover, all the details of the invention may be substitutedby technically equivalent elements.

Unless specified otherwise, any of the feature or characteristics of anyone of the embodiments of the apparatus and method for flowequipartition disclosed herein may be combined with the features orcharacteristics of any other embodiments of the apparatus and method forflow equipartition.

Those skilled in the art will recognize that a wide variety ofmodifications, alterations, and combinations can be made with respect tothe above described embodiments without departing from the scope of theinvention, and that such modifications, alterations, and combinationsare to be viewed as being within the ambit of the inventive concept.

The patent claims at the end of this patent application are not intendedto be construed under 35 U.S.C. § 112(f) unless traditionalmeans-plus-function language is expressly recited, such as “means for”or “step for” language being explicitly recited in the claim(s). Thesystems and methods described herein are directed to an improvement tocomputer functionality, and improve the functioning of conventionalcomputers.

What is claimed is:
 1. A system, comprising: a first pressure-adjustingdevice that is positioned in a first line, wherein the firstpressure-adjusting device is actuated solely via a first pneumaticsignal that is output from a first pilot valve to control a downstreampressure in the first line; and a second pressure-adjusting device thatis positioned in a second line, wherein the second pressure-adjustingdevice is actuated via the first pneumatic signal in a first mode ofoperation and via a second pneumatic signal that is output from a secondpilot valve in a second mode of operation to control a downstreampressure in the second line.
 2. The system of claim 1, wherein in thesecond mode of operation, the downstream pressure in the second line isless than the downstream pressure in the first line.
 3. The system ofclaim 1, further comprising a pneumatic connection conduit, thepneumatic connection conduit connecting the first pilot valve and thesecond pressure-adjusting device to determine a pressure equal to thedownstream pressure in the first line.
 4. The system of claim 3, furthercomprising a pneumatic switch positioned along the pneumatic connectionconduit, the pneumatic switch being adapted to interrupt the connectionbetween the first pilot valve and the second pressure-adjusting device.5. The system of claim 4, wherein the pneumatic switch is adapted toremain normally open for downstream pressure values in the first linethat are greater than or equal to a first predetermined pressuredetermined by the first pilot valve or a second predetermined pressuredetermined by the second pilot valve.
 6. The system of claim 4, furthercomprising a controller adapted to control the pneumatic switch byselectively activating closure of the pneumatic switch.
 7. The system ofclaim 6, wherein the controller is a pneumatic controller and comprisesa pneumatic feeding conduit to feed the pneumatic switch, the pneumaticfeeding conduit being connected to the first line to feed gas thereto.8. The system of claim 7, wherein the pneumatic switch comprises amembrane and a spring, the spring adapted to oppose a force generated byaction of the gas pressure acting on the membrane.
 9. The system ofclaim 6, wherein the controller is an electrical controller comprising:a pressure sensor positioned along the first line for feeding gasthereto; an electric actuator positioned inside the pneumatic switch;and an electrical circuit connecting the sensor and the electricactuator; wherein the circuit comprises a control unit to activate theelectric actuator and close the pneumatic switch when the sensordetects, on the first line, a pressure value less than a firstpredetermined pressure determined by the first pilot valve.
 10. Amethod, comprising: positioning a first pressure-adjusting device in afirst line, wherein the first pressure-adjusting device is actuatedsolely via a first pneumatic signal that is output from a first pilotvalve to control a downstream pressure in the first line; andpositioning a second pressure-adjusting device in a second line, whereinthe second pressure-adjusting device is actuated via the first pneumaticsignal in a first mode of operation and via a second pneumatic signalthat is output from a second pilot valve in a second mode of operationto control a downstream pressure in the second line.
 11. The method ofclaim 10, further comprising: connecting, via a pneumatic connectionconduit, the first pilot valve and the second pressure-adjusting device;and determining, via the first pilot valve, a pressure equal to thedownstream pressure in the first line.
 12. The method of claim 11,further comprising: positioning a pneumatic switch along the pneumaticconnection conduit, wherein the pneumatic switch is adapted to interruptthe connection between the first pilot valve and the secondpressure-adjusting device
 13. The method of claim 12, further comprisingconfiguring the pneumatic switch to remain normally open for downstreampressure values in the first line that are greater than or equal to afirst predetermined pressure determined by the first pilot valve or asecond predetermined pressure determined by the second pilot valve. 14.The method of claim 12, further comprising controlling, via acontroller, the pneumatic switch by selectively activating closure ofthe pneumatic switch.
 15. The method of claim 14, wherein the step ofcontrolling the pneumatic switch via the controller comprisescontrolling the pneumatic switch via a pneumatic controller having apneumatic feeding conduit that feeds the pneumatic switch and that isconnected to the first line to feed gas thereto.
 16. The method of claim15, wherein the step of controlling the pneumatic switch via thecontroller comprises: generating, via a gas pressure, a force that actson a membrane; and opposing the force acting on the membrane via aspring.
 17. The method of claim 14, wherein the step of controlling thepneumatic switch via the controller includes controlling the pneumaticswitch via an electric controller by feeding gas to the first line via apressure sensor positioned along the first line; and actuating anelectrical circuit with a control unit that activates an electricactuator and closes the pneumatic switch upon the pressure sensordetecting a pressure value that is less than a first predeterminedpressure determined by the pilot valve.
 18. A method for controlling asystem having a first pressure-adjusting device positioned in a firstline, a second pressure-adjusting device positioned in a second line, afirst pilot valve that outputs a first signal, and a second pilot valvethat outputs a second signal, the method comprising: controlling adownstream pressure in the first line by actuating the firstpressure-adjusting device solely via the first pneumatic signal outputfrom the first pilot valve; in a first mode of operation, controlling adownstream pressure in the second line by actuating the secondpressure-adjusting device via the first pneumatic signal output from thefirst pilot valve; and in a second mode of operation, controlling thedownstream pressure in the second line by actuating the secondpressure-adjusting device via the second pneumatic signal output fromthe second pilot valve.
 19. The method of claim 18, further comprisingthe step of: interrupting a connection between the first pilot valve andthe second pressure-adjusting device
 20. The method of claim 19, furthercomprising maintaining a pneumatic switch in a normally openconfiguration when downstream pressure values in the first line aregreater than or equal to a first predetermined pressure determined bythe first pilot valve or a second predetermined pressure determined bythe second pilot valve.